Re: Recover from "couldn't read tree root"?

On Sun, Jun 20, 2021 at 2:38 PM Nathan Dehnel [off-list ref] wrote:

A machine failed to boot, so I tried to mount its root partition from
systemrescuecd, which failed:

[ 5404.240019] BTRFS info (device bcache3): disk space caching is enabled
[ 5404.240022] BTRFS info (device bcache3): has skinny extents
[ 5404.243195] BTRFS error (device bcache3): parent transid verify
failed on 3004631449600 wanted 1420882 found 1420435
[ 5404.243279] BTRFS error (device bcache3): parent transid verify
failed on 3004631449600 wanted 1420882 found 1420435
[ 5404.243362] BTRFS error (device bcache3): parent transid verify
failed on 3004631449600 wanted 1420882 found 1420435
[ 5404.243432] BTRFS error (device bcache3): parent transid verify
failed on 3004631449600 wanted 1420882 found 1420435
[ 5404.243435] BTRFS warning (device bcache3): couldn't read tree root
[ 5404.244114] BTRFS error (device bcache3): open_ctree failed

btrfs rescue super-recover -v /dev/bcache0 returned this:

parent transid verify failed on 3004631449600 wanted 1420882 found 1420435
parent transid verify failed on 3004631449600 wanted 1420882 found 1420435
parent transid verify failed on 3004631449600 wanted 1420882 found 1420435
parent transid verify failed on 3004631449600 wanted 1420882 found 1420435
parent transid verify failed on 3004631449600 wanted 1420882 found 1420435
Ignoring transid failure
ERROR: could not setup extent tree
Failed to recover bad superblocks

uname -a:

Linux sysrescue 5.10.34-1-lts #1 SMP Sun, 02 May 2021 12:41:09 +0000
x86_64 GNU/Linux

btrfs --version:

btrfs-progs v5.10.1

btrfs fi show:

Label: none  uuid: 76189222-b60d-4402-a7ff-141f057e8574
        Total devices 10 FS bytes used 1.50TiB
        devid    1 size 931.51GiB used 311.03GiB path /dev/bcache3
        devid    2 size 931.51GiB used 311.00GiB path /dev/bcache2
        devid    3 size 931.51GiB used 311.00GiB path /dev/bcache1
        devid    4 size 931.51GiB used 311.00GiB path /dev/bcache0
        devid    5 size 931.51GiB used 311.00GiB path /dev/bcache4
        devid    6 size 931.51GiB used 311.00GiB path /dev/bcache8
        devid    7 size 931.51GiB used 311.00GiB path /dev/bcache6
        devid    8 size 931.51GiB used 311.03GiB path /dev/bcache9
        devid    9 size 931.51GiB used 311.03GiB path /dev/bcache7
        devid   10 size 931.51GiB used 311.03GiB path /dev/bcache5

Is this filesystem recoverable?

quoted

(Sorry, re-sending because I forgot to add a subject)

Definitely don't write any irreversible changes, such as a repair
attempt, to anything until you understand what what wrong or it'll
make recovery harder or impossible.

Was bcache in write back or write through mode?

What's the configuration? Can you supply something like

lsblk -o NAME,FSTYPE,SIZE,FSUSE%,MOUNTPOINT,UUID,MIN-IO,SCHED,DISC-GRAN,MODEL



-- 
Chris Murphy